We herein propose to continue our exploration of the chemistry of specifically designed nitrogen heteromacrocyclic compounds in order to ascertain their potential as biological models. We propose specifically to: (1) design new synthetic routes to pyridine-containing heteromacrocycles which possess a rigid non-flexible framework of known structural constraints which are similar to the corrin and porphyrin skeletal backbones; (2) determine the selective metal ion coordination and general ligand potential of these macrocycles; (3) study the unique electronic and structural relationships between these proposed macrocyclic models and known biological tetropyrrole systems; (4) ascertain the possible substitution of non-metal bonded complexes for more intricate heme-containing proteins; and (5) elucidate the specific binding site properties as a factor in the action of mitochondrial electron-transfer, redox reactions, and semiconduction. The chemistry of the basic macrocyclic skeletons will be conducted through partial reduction (chemical and electrochemical) and substitution reactions, which will permit functionalization of the periphery as well as synthesize the novel metalloheteromacrocycles. Biochemical in vitro antimicrobial and anthelmintic activity studies as well as to identify the effects of singlet-oxygen toxicity on mouse leukaemia L 1210 cells will be considered with the aid of our microbiology department.